Speed sensor ring

ABSTRACT

The invention relates to a signal inducing device ( 1, 9, 11, 12, 18, 19, 20 ), comprising a first material ( 2, 3, 13, 14 ) and a second material ( 4, 16 ). The first material ( 2, 3, 13, 14 ) and the second material ( 4, 16 ) show a different magnetic behaviour. The first material ( 2, 3, 13, 14 ) and the second material ( 4, 16 ) are arranged in a way that the resulting magnetic behaviour of the signal inducing device ( 1, 9, 11, 12, 18, 19, 20 ) varies over a magnetic interaction surface ( 5, 10 ) of the signal inducing device ( 1, 9, 11, 12, 18, 19, 20 ). The signal inducing device ( 1, 9, 11, 12, 18, 19, 20 ) is designed in a way that the magnetic interaction surface ( 5, 10 ) shows an essentially smooth surface, in particular with respect to the standard moving direction of the magnetic interaction surface ( 5, 10 ).

CROSS REFERENCE TO RELATED APPLICATION

Applicant hereby claims foreign priority benefits under U.S.C. §119 fromGerman Patent Application No. 102015117498.7 filed on Oct. 14, 2015, thecontent of which is incorporated by reference herein.

TECHNICAL FIELD

The invention relates to a signal inducing device, comprising a firstmaterial and a second material, wherein the first material and thesecond material show a different magnetic behaviour, and wherein thefirst material and the second material are arranged in a way that theresulting magnetic behaviour of the signal inducing device varies over amagnetic interaction surface of the signal inducing device.

BACKGROUND

Signal inducing devices, sometimes referred to as speed sensor rings arefrequently used for a plethora of technical devices. As an example, theyare used to determine the speed, and sometimes even a position, of adevice that is turning with respect to a (main) part of a machine beingat rest.

An example for this is a turning axle of a vehicle (where wheels areattached to) or a crankshaft of a combustion engine.

Due to the wide and frequent use of such speed sensor rings, a hugevariety of speed sensor rings is known in the state of the art which allwork reasonably well.

Sometimes, however, problems arise in some special technicalapplications that are not known in the context of other technicalapplications (although they sometimes seem to be closely related witheach other).

As an example, toothed wheels made of a soft magnetic material arefrequently used as a signal inducing device for a magnetic sensor, wherethe combination of the toothed wheel and the sensor are used fordetermining the turning speed of an axle that is connected to a wheel.Such an arrangement is used for determining the speed of a vehicleand—as a more elaborate example—as a sensor arrangement for an anti-locksystem for breaking (which relates to speed information as well). Whilesuch an arrangement is working well for a lot of applications, problemscan occur, if the device is used for hydraulic systems. Here, thepresence of oil near the signal inducing device is almost unavoidable.Sometimes, the toothed wheel has to be arranged in an area of thevehicle, where the toothed wheel is partially or even fully immersed inhydraulic oil. Now, the problem arises that the teeth and the gapsbetween the teeth produce a hydraulic friction in the oil bath. Inparticular at higher turning speeds of the axle/toothed wheel, asignificant loss of mechanical energy (and consequently an appropriatelyhigh generation of thermal energy) will occur when using such a toothedwheel. Of course, this adverse behaviour is to be avoided.

For such applications, an alternative solution has been suggested, wherean elastic band is used as a base for a signal inducing device. Atregular intervals, a magnetic coating is arranged of the base material.Afterwards, a thin coating is applied to the outer surface of the deviceto make the surface as smooth as possible. A disadvantage of thissolution is that still some roughness exists on the outside.Furthermore, the device is quite cost intensive to produce. Yet anotherdisadvantage is the use of magnetic material (hard magnetic material tobe exact). When the material is magnetised, it is prone to agglomerationof soft or hard magnetic materials. However, such materials can bearound in form of small metallic particles in the hydraulic oil, wherethe small metallic particles can be present due to wear of metalliccomponents. This can even lead to a destruction of the sensor. It iseasy to understand that this is not what one is looking for.

SUMMARY

Therefore, the object of the invention is to propose a signal inducingdevice that shows a varying magnetic behaviour over a magneticinteraction surface of the signal inducing device that is improved oversignal inducing devices that are known in the state of the art. A signalinducing device according to claim 1 solves this object.

It is suggested to design a signal inducing device, comprising a firstmaterial and a second material, wherein the first material and a secondmaterial show a different magnetic behaviour and wherein the firstmaterial and the second material are arranged in a way that theresulting magnetic behaviour of the signal inducing device varies over amagnetic interaction surface of the signal inducing device in a way thatthe signal inducing device is designed in a way that the magneticinteraction surface shows an essentially smooth surface, in particularwith respect to the standard moving direction of the magneticinteraction surface. Albeit more materials can be used, it is preferredif exactly two different materials are used for the signal inducingdevice and/or in the vicinity of the magnetic interaction surface of asignal inducing device. The magnetic behaviour can vary in various ways.As an example, a different magnetic behaviour with respect to theunderlying physical effect of the respective material can be envisaged.To elucidate this, the first material can be a paramagnetic substance ora diamagnetic substance, while the second material can be aferromagnetic substance. However, different combinations are possible aswell. In particular, when it comes to ferromagnetic substances, adifferentiation between hard magnetic substances (presumably showing apermanent magnetism and/or not showing a permanent magnetism per se) andsoft magnetic substances can be made. Due to the limited magnetic effectof paramagnetic and diamagnetic substances, both can be considered to be(essentially) non-magnetic substance (in particular within the contextof the present application and/or invention). Another differentiationbetween different magnetic behaviour can be made based on the strengthof the respective effect. As an example, both first and second materialcan be a ferromagnetic substance, while the first material is a softmagnetic material and the second material is a hard magnetic material(or the like). It is even possible, that the first and the secondmaterial are taken from the group, showing the same “underlying physicaleffect”, while they differ in “strength of the respective effect”. As anexample, both first and second material can be soft magnetic material.However, it is possible that the first material shows a lower (relative)magnetic susceptibility with respect to the second material (or viceversa). Furthermore, it should be noted that “first material” and“second material” cannot only be understood in the sense that different“pure” substances are used. Of course, it is possible that one or bothof the materials involved are composites comprising a mixture ofdifferent materials (for example an alloy or a ceramic substance). Ineffect, it is even possible that the first material and the secondmaterial are to be understood to be a mixture of the same components,but the ratio of the different components is different. The “resultingmagnetic behaviour” can be particularly understood as the “combinedmagnetic effect” at a certain location with respect to the signalinducing device, in particular with respect to the magnetic interactionsurface. Typically, said certain location is a position, where a sensor(in particular a magnetic sensor) will be typically arranged whenemploying the signal inducing device in its intended place in a morecomplex machine (including the respective sensor). It is to be notedthat said certain position (i.e. where typically a sensor is placed)will usually move with respect to the signal inducing device (or to bemore exact: typically the signal inducing device will move with respectto the certain position; in particular a position where a sensor isplaced). The certain position where the measurement is taken (inparticular location of a sensor) is typically considered with respect toa reference frame of the more complex machinery, the signal inducingdevice is used in. In this reference frame, the certain position (of thesensor) is at rest. As an example: if the signal inducing device (andpresumably the sensor) is used in a vehicle, the reference frame of thevehicle is typically moving with respect to factory building, of course.Therefore, both the signal inducing device and the sensor of a vehicleare typically moved with respect to the factory building, while thesensor is resting with respect to the vehicle's body. Furthermore, theresulting magnetic behaviour of the signal inducing device can change inessentially every thinkable way. Not only a (absolute) value like themagnetic susceptibility and/or the (absolute) strength of a permanentmagnetic field might vary, but also additionally and/or alternatively adirection of a susceptibility, a direction of a permanent magnetic fieldand so on. According to the present suggestion, the signal inducingdevice is designed in a way that the magnetic interaction surface showsan essentially smooth surface, in particular with respect to thestandard moving direction of the magnetic interaction surface. Thesmooth surface is usually to be understood with respect to fluid dynamicforces that occur when moving the essentially smooth surface withrespect to the fluid the essentially smooth surface (magneticinteraction surface) comes into contact when the signal inducing deviceis used in its intended machinery. As an example, when the signalinducing device is partially immersed in hydraulic oil, when it isarranged in the gearbox of a forklift truck (to give an example), themagnetic interaction surface will come into contact with air (at ambientair pressure; typically at around approximately 1 bar air pressure,depending on weather conditions and altitude, of course) and hydraulicoil (at the same pressure level as the air “above”). Therefore, anessentially smooth surface should generate comparatively small viscousforces when being in contact with air and hydraulic oil, when the signalinducing device is moving in its standard moving direction. Therefore,dimples that are used for generating a lotus effect (to give an example)can be considered to be “an essentially smooth surface” in the presentcontext, albeit from a strictly geometrical viewpoint, this is of coursenot a smooth surface. Therefore, the expression of “an essentiallysmooth surface” with respect to the standard moving direction of themagnetic interaction surface might be considered to be a surface,showing low forces (in particular viscous forces or dampening forces)when moving with respect to a fluid (or even more fluids) the magneticinteraction surface of the signal inducing device is designed to be incontact with (in particular under standard operating conditions of thesignal inducing device). In general, a fluid in the sense of thisapplication can be a gas, a liquid or a mixture of both. In particular,it is even possible that some solid particles are contained (likesmoke=a gas, containing solid particles or a suspension=a liquid,containing solid particles). Consequently, it shall be allowed to useboth definitions (and presumably slight variations and/or preferredembodiments thereof) alternatively, in combination and/orinterchangeably. As an additional remark, it should be mentioned thatthe signal inducing device can have more than one standard movingdirection of the magnetic interaction surface. A typical example is theuse of a signal inducing device on the axle of a driving wheel of aforklift truck. The forklift truck can of course be driven in twodirections (forward and backward direction). So the signal inducingdevice can be designed in a way, that it shows an essentially smoothsurface when being moved in both directions (i.e. forward and backward).Using the example of a forklift truck, it is preferred if the smoothsurface shows the same quality/quantity with respect to smoothness inboth directions (since a forklift truck is typically used in the forwardand the backward direction at similar speeds and for comparabledistances). Of course, it is also possible that a differentquality/quantity of this surface smoothness can be present for differentdirections. As an example, a car is typically used in the forwarddirection. In this direction the smoothness should be very high. Thebackward direction is however only used very infrequently and thequality of the smoothness in this direction can be very low withoutcausing any significant adverse effects. Nevertheless, even thisdirection can be somehow considered, so that the “quality/quantity ofthe essentially smooth surface” can be weighted in the differentdirections that are typically employed. Only for clarification: it is ofcourse possible that the signal inducing device can be operated in evenmore directions; nevertheless the standard application will be amovement in a forward and a backward direction (thus, these are thedirections that have to be considered at least at a higher degree).

It is preferred if the first material and the second material of thesignal inducing device are arranged alternately along the magneticinteraction surface of the signal inducing device, in particular along astandard moving direction of the magnetic interaction surface. Some kindof blocks, following each other, can be arranged on an outercircumference of a ring-like structure, for example. Using the suggesteddesign, a particularly profound change of the resulting magneticbehaviour at a point of measurement (for example a position of thesensor) can be realised very effectively. Of course, the distances anddimensions of the materials employed (in connection with the “degreeand/or direction of change of magnetic behaviour” of the material used)should be chosen in a way that they comply with the dimensions of thesignal inducing device and/or the position of the point of measurementand the like. This way, a particularly simple and efficient design canbe realised.

Another preferred embodiment can be realised if essentially all exposedsurfaces of the signal inducing device show an essentially smoothsurface, in particular with respect to the standard moving direction ofthe signal inducing device. Such a design normally does not counteractwith manufacturing processes and/or typically does not increase theoverall cost of the signal inducing device. However, using the suggesteddesign, the signal inducing device can be used more universally and inparticular can be used in connection with even strongly changingoperating conditions. As an example, when using a signal inducing deviceof the suggested design, the signal inducing device can be used inconnection with different fluid levels in the gearbox of a forklifttruck, when used under the aforementioned conditions. This way, thedevice can be used more universally.

Furthermore, it is suggested to design the signal inducing device in away that the magnetic interaction surface is designed as a closedsurface, in particular as a rounded surface, preferably as a circularsurface and/or in that the signal inducing device is designed as aring-like object and/or a wheel-like object. Using such a design, thesignal inducing device will typically show low counteracting viscousforces by its very design. Furthermore, such a shape will comply withtypical requirements the signal inducing device is typically used inconnection with. Since the suggested shapes are somewhat according to ausual design for signal inducing devices, the proposed signal inducingdevice can be used as a “snap-in” solution, which can increase theacceptance of the device.

Furthermore, it is suggested to design the signal inducing device in away that the signal inducing device is essentially symmetrical,preferably mirror symmetrical, in particular with respect to geometryand/or with respect to magnetic behaviour and/or in particular withrespect to a plane that lies normal to the standard moving direction ofthe signal inducing device and/or the standard moving direction of themagnetic interaction surface. Such a design complies with standardrequirements of signal inducing devices and is generally preferred. Inparticular, the respective device can be used as a “snap-in” solution,increasing the acceptance of the presently proposed signal inducingdevice. Furthermore, the respective design can lower viscous forcesand/or can increase the smoothness of the respective surfaces, which isof course advantageous.

Is further suggested to design the signal inducing device in a way thatbulges and/or notches are arranged along an exposed surface of thesignal inducing device, preferably along the magnetic interactionsurface, wherein preferably said bulges and/or notches are arranged in away that they show an essentially smooth surface with respect to thestandard moving direction of the signal inducing device and/or of themagnetic interaction surface. Such a design is particularly preferred,since the signal inducing device can be adapted very well to essentiallyany geometrical requirements of the machinery, the signal inducingdevice is intended to be used in. It is to be noted that available spaceis typically rare in nowadays machinery, in particular if the respectivemachinery is designed to be portable/mobile (for example whenconstructing a vehicle like a car or a forklift truck). Despite of thedegree of freedom of the geometrical shape, the respective surfacesstill can show a high degree of smoothness and consequently show no (orlittle, if any) increase of viscous forces when being employed.

Another preferred design can be realised if the signal inducing deviceis designed in a way that the first material comprises a soft magneticmaterial and/or a hard magnetic material and/or a material that is takenfrom the group comprising iron, iron alloys, steel and ferrites and/orin a way that the second material comprises a non-magnetic materialand/or comprises a material that is taken from the group comprisingresin, plastics, plastomers, nickel, nickel alloys, copper and copperalloys. First experiments have shown that such a design is particularlyadvantageous. In particular, if a material is used that shows no (orlittle) permanent magnetism, an agglomeration of metallic particlesaround the signal inducing device can be avoided, which is particularlyadvantageous. Furthermore, if a (soft and/or hard) magnetic material isused in combination with a non-magnetic material, a particular profoundchange of the resulting magnetic behaviour (at the sensor's position)can be realised along the magnetic interaction surface of the signalinducing device. Therefore, a simpler and less sensitive sensor can beemployed. Furthermore, if iron, steel or the like is used as a “basesubstance” of the signal inducing device, a particularly stable signalinducing device can be realised, since metals or the like typically showa high strength and are comparatively cheap and/or are easily available.Furthermore, they are standard material for a lot of technicalapplications.

It is furthermore suggested to design the signal inducing device in away that the first material and/or the second material show a bar-likeconfiguration along the magnetic interaction surface, preferably overthe full extent across the magnetic interaction surface. Firstexperiments have shown that such a design shows a particularlyadvantageous behaviour and is still comparatively easy to realise. Theexpression “bar-like configuration” can be interpreted in a broad sense.In particular, cubical-shaped or ashlar-formed shapes are possible.However, different forms are possible as well. In particular, a circularor elliptical cross-section, a (double-)dovetail shaped cross-section, atriangular-shaped cross-section and/or a rhomboid-shaped cross-section(along one or two planes, where those planes are preferablyperpendicular to each other, and where one plane lies preferablyessentially parallel to the plane of the ring/plate of the signalinducing device) are possible. In particular a (double-)dovetail-shapedform can be advantageous for improving the mechanical stability of thesignal inducing device.

It is further preferred to design the signal inducing device in a waythat at least one of the first and second material is arranged as atoothed rack and/or in that at least one of the first and secondmaterial is arranged as a filler material for indentations, inparticular for the spaces between the teeth of a toothed rack. In case awheel-like structure is used for the signal inducing device, a toothedwheel can be used and/or the spaces between the teeth of a toothed wheelcan be used. First experiments have shown that this way a particularlycheap and yet very stable signal inducing device, showing advantageouseffects can be realised. In particular, using the suggested device, itis usually possible to use standard components that are already aroundand are readily available. The teeth of the toothed rack can haveessentially any shape. In particular, a rectangular, a sawtooth-likeand/or a triangular shaped toothed rack and/or a toothed rack showing“rounded teeth” is possible.

It is further suggested to design the signal inducing device in a waythat the first material and the second material are connected to eachother by means of a force-fit connection, by means of a form-lockingconnection, by means of a positive substance locking connection orcombinations thereof (combining two of the aforementioned connections oreven all three). As a positive substance locking connection, gluing,soldering or welding can be used, as an example. It should be noted thatall of the connections mentioned (i.e. force-fit connection and/orform-locking connection and/or positive substance locking connection)cannot be only established with the first material and the secondmaterial involved. Instead, it is also possible to use a third materialfor performing at least part of the “connection work”. As an example, ifa toothed wheel that is possibly made a soft magnetic material (likeiron or an iron alloy) is used as the “start” of the signal inducingdevice, the gaps between the teeth of the tooth wheel can be later onfilled by a plastic material (or another preferably non-magneticmaterial). These fillings can hold in place by adhesive forces (usingglue for example) and/or by forming somehow an inlay connection as it isknown from dentistry. Later on, some additional fixation like aresilient coating, covering both the first and the second material, canbe applied, reinforcing the overall device.

Another preferred embodiment can be realised if the first materialand/or the second material are spaced evenly and/or in that the firstmaterial and/or the second material are spaced in a special encodingarrangement and/or in that the signal inducing device, in particular thefirst material and/or the second material is/are designed and/or is/arearranged in a way that the magnetic interaction surface produces anessentially binary signal. Choosing an embodiment according to thesuggestion, the signal inducing device can be used for typicalrequirements. For example, the signal inducing device can be used for asimple measurement of speed (for example rotational speed of an axle).However, using a special encoding, it is also possible to determine theposition of the signal inducing device (which can be an axle of a wheelor a crankshaft of an engine or the like). Typically, it is preferred ifthe resulting signal is of a binary type. This is not only because theresulting logic is usually easier to implement. In addition, if thesignal is of a binary type, aggregations of dirt, alterations of thedevices or the like usually do not play a relevant role (where in caseof the value of an analogue signal is used, where the value containssome information, this will usually result in “bad readings”).

Furthermore a signal inducing arrangement is proposed, comprising asignal inducing device of the aforementioned type and a sensor device.In particular, the signal inducing device and the sensor device arecombined in a “sensible way”. In particular, this usually means that inthe present proposed device, the sensor will read the (varying) magneticbehaviour of the signal inducing device along a magnetic interactionsurface thereof. Furthermore, the arrangement and the positions of bothdevices will be chosen in a way that a good signal will be produced bythe sensor and/or in a way that no adverse mechanical effects (forexample an impact or the like) will occur, at least under standardoperating conditions.

In particular, the signal inducing device and/or the signal inducingarrangement according to the previous description can be used for anykind of rotating device. In particular, the rotating device can be anaxle, a crankshaft, a wheel, a wheel support, a spindle device and/or ashaft of essentially any type of machinery. The machinery can be (toname some examples) a motor, a combustion engine, a machine tool, anelectric motor, an electric generator, a fluid working machine, a fluidpump, a fluid motor (where the fluid can be hydraulic oil and/or waterin both cases), a turbine, a carriage device, an undercarriage device, agenerator device, a wind generator device or the like. The signalinducing device and/or the signal inducing arrangement can be used forstationary machinery, land craft (including on-road use, off-road useand/or rail-bound use), watercraft, aircraft and/or spacecraft. Inparticular vehicles like cars, trucks, buses, vehicles comprisinghydraulic installations, forklift trucks, tractors, farm machinery andthe like are possible.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features, and objects of the invention will beapparent from the following detailed description of the invention inconjunction with the associated drawings, wherein the drawings show:

FIG. 1 is a first embodiment of a speed sensor ring in a schematicperspective view;

FIG. 2A shows the first embodiment of a speed sensor ring in a partialview;

FIG. 2B shows the first embodiment of the speed sensor ring in a partialcross-sectional view;

FIG. 3A is a second embodiment of a speed signal ring in a partial viewfrom the side;

FIG. 3B shows the second embodiment of the speed signal ring in apartial cross-sectional view;

FIG. 4 is a third embodiment of a speed sensor ring in a cross-sectionalview;

FIG. 5A shows another embodiment of a speed sensor ring in a sectionaltop view and a sectional cross-sectional view, respectively;

FIG. 5B shows another embodiment of a speed sensor ring in a sectionaltop view and a sectional cross-sectional view, respectively;

FIG. 5C shows another embodiment of a speed sensor ring in a sectionaltop view and a sectional cross-sectional view, respectively;

FIG. 6A is a first step of a possible production scheme for a speedsensor ring.

FIG. 6B shows a second step of the production scheme of FIG. 6A; and

FIG. 6C shows an optional third step of the production scheme of FIG.6A.

DETAILED DESCRIPTION

In FIG. 1, a possible first embodiment of a speed sensor ring 1 is shownin a schematic perspective view. The speed sensor ring 1 can vary insize significantly depending on the application. However, in thepresently shown embodiment, the speed sensor ring has a width of 1.5 cm(axial dimension) a diameter of 15 cm (outer radial dimension) and athickness of the ring structure of 1.5 cm. Further details of the designof the speed sensor ring 1 can be seen in FIG. 2, where a partial sideview and a cross-sectional view through the speed ring 1 are shown.

This speed sensor ring 1 comprises a base body 2 that has the basicdesign of a tooth wheel with essentially rectangular teeth 3 (of course,the “tooth wheel” is presently not a wheel, but a ring, so the “innerplate” is missing; however, the speed sensor ring 1 could also have thedesign of a wheel). The rectangular teeth 3 have a circumferentiallength (seen when going along the radius) of presently 3 mm. Thedistance between two teeth 3 is presently 5 mm. The gaps between twoconsecutive teeth 3 are filled with a filling 4. The fillings 4 aredimensioned in a way that an essentially smooth surface (outercircumferential surface 5) is established, when the speed sensor ring 1is turned (for example when being placed on a driving axle of a forklifttruck). This way, a turning movement of the speed sensor ring 1 will notinduce (significant) friction/decelerating (viscous) forces when thespeed sensor ring 1 is (partially) immersed in hydraulic oil, forexample.

To be more exact, the outer circumferential surface 5 and both sidewalls6 of the speed sensor ring 1 have to have a smooth surface. In thepresently shown embodiment, even the inner circumferential surface 7 ofthe speed sensor ring 1 is designed with a smooth surface. However, thiscan be different as well. As an example, the inner circumferentialsurface 7 can show some recesses or protrusions (ridges or ditches) thatare extending in an axial direction. These recesses or protrusions canengage corresponding protrusions/recesses that are arranged on the outercircumference of an axle to form a form-fit connection between the axleand the speed sensor ring. If this is designed in an appropriate way, no“rough surfaces” will be “visible” from the outside (for example forhydraulic oil).

However, if the present design of a smooth inner circumferential surface7 is used, normally the handling and the assembly of the speed sensorring 1 will be particularly simple. An attachment on an axle can be doneusing glue, for example.

In the presently shown example, the fillings 4 will hold in placebetween the rectangular teeth 3 using glue. In particular, if theturning speed of the speed sensor ring 1 is not excessive, such a methodof attachment will usually be sufficient to counter tangential forcesinduced by turning the speed sensor ring 1. The thickness of thefillings 4 (and therefore the depths of the gaps between two teeth 3) ispresently 2.5 mm.

In the presently shown example, the base body 2 of the speed sensor ring1 is made of a soft magnetic material, presently an iron alloy or steel.On the contrary, the fillings 4 (presently made of a plastic material)are made of a non-metal material. Therefore, a quite distinct differencebetween the magnetic behaviour of both materials 3, 4 along the outercircumferential surface 5 (magnetic interaction surface), and thus ofthe resulting magnetic behaviour in the vicinity of the outercircumferential surface 5 of the speed sensor ring 1 is present.

It should be noted, that not only a plastic material can be used as anon-magnetic material, but also different materials, in particular evennon-magnetic metals (like aluminium, copper, brass) could be used aswell.

An advantage of using non-magnetic material together with soft magneticmaterial is that no (strong) permanent magnetic field will be generatedby the speed sensor ring 1. This is very advantageous, because smallmetallic particles (some smaller steel chips due to wear or the like)that might be around will not be picked up by the speed sensor ring(missing magnetic forces). Therefore, an “aggregation of surfaceroughness with time” can be effectively avoided.

Nevertheless, it should be noted as well that the speed sensor ring 1could be (partially) manufactured from magnetisable material (hardmagnetic material) and/or magnetised material (permanent magnets).

As it is schematically indicated in FIG. 1, a magnetic sensor 8 can beplaced near the outer circumferential surface 5 (magnetic interactionsurface of the signal inducing device), so that it will pick up changesin the resulting magnetic behaviour of the speed sensor ring 1 along itsouter circumferential surface 5. This way, the turning speed of thespeed sensor ring 1 can be determined.

It should be noted that in the present example, the spaces between twoconsecutive teeth 3 and/or two consecutive fillings 4 are identicalalong the circumference of the speed sensor ring 1. Therefore,additional means for determining a turning direction and/or the positionof the device the speed sensor ring 1 is used for (for example of anaxle) has to be determined by different means.

Alternatively, a design for the speed sensor ring 1 could be used, wheredifferent sizes of the teeth 3/fillings 4 are used in a way that adistinct pattern is formed, so that the turning direction and/or theposition of the speed sensor ring 1 can be determined by said pattern bymeans of the sensor 8.

As can be seen particularly from FIG. 2b , the axial extent of thefillings 4 is chosen in a way that the fillings 4 extend over the wholeaxial dimension of the speed sensor ring. Of course, different designsare possible as well, like a sidewall, generated by the base body 2 onone or on both sides 6 of the speed sensor ring 1. Likewise, thefillings 4 could have an axial (and/or radial) extension that willinterconnect the fillings 4 along one or both sidewalls 6 and/or alongthe outer circumferential surface 5.

In FIG. 3, a second embodiment of a speed sensor ring 9 is shown. InFIG. 3, a partial side view (FIG. 3a ) and a cross-section (FIG. 3b )through the speed sensor ring 9 is shown.

As can be seen, the speed sensor ring 9 has a tapered surface 10 that isarranged between one of the sidewalls 6 (right sidewall in FIG. 3b ) andthe outer circumferential surface 5 of the speed sensor ring 9.

In the presently shown embodiment, the tapered surface 10 is arrangedand dimensioned in a way that near one of the sidewalls 6 (rightsidewall in FIG. 3b ), a “protrusion” of the base body 2 will be presentin the axial direction of the speed sensor ring 9. Therefore, it in atop view, looking onto the outer circumferential surface 5 of the speedsensor ring 9, a “band” of the base body 2 will be visible near therespective sidewall 6.

The presently shown second embodiment of the speed sensor ring 9 can beadvantageous for certain arrangements. In particular, it might be thecase that due to limited available space and/or due to geometricalconsiderations, the sensor 8 has to be arranged somewhat “sideways” fromthe speed sensor ring 9. This arrangement of the sensor 8 isschematically shown in FIG. 3 b.

As it is clear from FIG. 3b , the magnetic interaction surface can nowbe considered to be the tapered surface 10. However, the outercircumferential surface 5 can still be used as a magnetic interactionsurface. It is even possible, that a sensor 8 is placed in the vicinityof a sidewall 6, so that even the sidewalls 6 (or one of them) can beconsidered to be a magnetic interaction surface.

Only for completeness, in FIG. 4 a third embodiment of a speed sensorring 11 is shown. Here, both sidewalls 6 show a tapered surfaceanalogous to the second embodiment of a speed sensor ring 9 (as seen inFIG. 3).

In FIG. 5, a set of additional three exemplary embodiments of a speedsensor ring 18, 19, 20 is shown in two different sectional views,respectively. The first view (top row of FIG. 5) is a view onto theouter circumferential surface of the respective speed sensor ring 18,19, 20, while the second view (bottom row of FIG. 5) is a sectionalcross-section through the respective speed sensor ring 18, 19, 20.

In the speed sensor ring 18, as shown in FIG. 5a , the respectivefillings 4 have an elliptical shape when seen from atop (outercircumferential surface 5 of the speed sensor ring 18), while some thinwalls 21 are comprised of the “base material” of the speed sensor ring18 remain on the sideward surface of the speed sensor ring 18.Therefore, when viewed from the side, one would see a continuous,uninterrupted surface of the speed sensor ring 18. When seen in across-sectional view (cross-sectional plane parallel to the plane of thespeed sensor ring 18), however, one can see the presently rectangularshaped fillings 4 (also a dove-tail shape or the like would be possibleas well). The cross-sectional view is depicted in the lower row of FIG.5 a.

In FIG. 5b , the speed sensor ring 19 has rectangular fillings 4, whenseen from atop (outer circumferential surface 5 of the speed sensor ring19). In the cross-sectional view, however, one can see a dove-tail shapeof the fillings 4. Thus, a form-locking connection between the fillings4 and the base material of the speed sensor ring 19 is realized. Even atvery high turning speeds of the speed sensor ring 19, the fillings 4will hold well in place due to this form-locking connection. Insertionof the fillings 4 can be made by pressure moulding methods, or bysliding in the respective fillings 4 from the side.

In FIG. 5c , the fillings 4 of the speed sensor ring 20 not only have adove-tail shape, when seen in the cross-sectional view, but also adouble-dovetail shape, when seen from atop (outer circumferentialsurface 5 of the speed sensor ring 20). This way, the fillings 4 holdvery well in place, even with respect to sideward forces. The fillings 4can be placed by pressure moulding methods, for example.

Finally, in FIG. 6 possible manufacturing steps for producing a speedsensor ring 12 are shown. The speed sensor ring 12 can be of a designaccording to one of the already presented embodiments (i.e. a speedsensor ring 1 according to the first embodiment, a speed sensor ring 9according to the second embodiment and/or a speed sensor ring 11according to the third embodiment and/or a speed sensor ring 18, 19, 20according to one of the additional three exemplary embodiments) and/orof a different design. In particular, the speed sensor ring can be awheel-like structure as well (then, one could even talk about a speedsensor disc or a speed sensor wheel).

First of all (FIG. 6a ), a base body 13 will be produced, showing anumber of (presently) evenly spaced teeth 14 (presently of a rectangulardesign; this could be different as well, however; in particular one hasto rethink slightly if one of the additional three embodiments of speedsensor rings 18, 19, 20 is employed), where between two consecutiveteeth 14, a gap 15 is arranged (presently of a rectangular design aswell).

Subsequently (FIG. 6b ) the gaps 15 between the teeth 14 are filled witha filler material 16 in a way that essentially smooth surfaces will begenerated (outer circumferential surface and/or sidewalls of the speedsensor ring 12). As an example, the fillings 16 can be assembled bypressure moulding or the like.

Finally, as an optional step (see FIG. 6c ), a coating 17 can be appliedto the outer circumferential surface and/or to one or both sidewalls.This way, some (typically minor) roughness of the outer surfaces can bereduced, minimised and/or (essentially) avoided. Furthermore, thestability of the speed sensor ring 12 might be increased as well byproviding a coating 17.

While the present disclosure has been illustrated and described withrespect to a particular embodiment thereof, it should be appreciated bythose of ordinary skill in the art that various modifications to thisdisclosure may be made without departing from the spirit and scope ofthe present disclosure.

What is claimed is:
 1. A signal inducing device, comprising a firstmaterial and a second material, wherein the first material and thesecond material show a different magnetic behaviour, wherein the firstmaterial and the second material are arranged in a way that theresulting magnetic behaviour of the signal inducing device varies over amagnetic interaction surface of the signal inducing device, wherein thesignal inducing device is designed in a way that the magneticinteraction surface shows an essentially smooth surface, in particularwith respect to the standard moving direction of the magneticinteraction surface.
 2. The signal inducing device according to claim 1,wherein said first material and said second material are arrangedalternately along the magnetic interaction surface of the signalinducing device, in particular along a standard moving direction of themagnetic interaction surface.
 3. The signal inducing device according toclaim 1, wherein essentially all exposed surfaces of the signal inducingdevice show an essentially smooth surface, in particular with respect tothe standard moving direction of the signal inducing device.
 4. Thesignal inducing device according to claim 1, wherein the magneticinteraction surface is designed as a closed surface, in particular as arounded surface, preferably as a circular surface and/or in that thesignal inducing device is designed as a ring-like object and/or awheel-like object.
 5. The signal inducing device according to claim 1,wherein the signal inducing device is essentially symmetrical,preferably mirror symmetrically, in particular with respect to geometryand/or with respect to magnetic behaviour, and/or in particular withrespect to a plane that lies normal to the standard moving direction ofthe signal inducing device and/or the standard moving direction of themagnetic interaction surface.
 6. The signal inducing device according toclaim 1, wherein bulges and/or notches are arranged along an exposedsurface of the signal inducing device, preferably along the magneticinteraction surface, wherein preferably said bulges and/or notches arearranged in a way that they show an essentially smooth surface withrespect to the standard moving direction of the signal inducing deviceand/or the magnetic interaction surface.
 7. The signal inducing deviceaccording to claim 1, wherein the first material comprises a softmagnetic material and/or a hard magnetic material and/or a material thatis taken from the group comprising iron, iron alloys, steel and ferritesand/or characterized in that the second material comprises anon-magnetic material and/or comprises a material that is taken from thegroup comprising resin, plastics, plastomers, nickel, nickel alloys,copper and copper alloys.
 8. The signal inducing device according toclaim 1, wherein the first material and/or the second material show abar-like configuration along the magnetic interaction surface,preferably over the full extent across the magnetic interaction surface.9. The signal inducing device according to claim 8, wherein at least oneof the first and second material is arranged as a toothed rack and/or inthat at least one of the first and second material is arranged as afiller material for indentations, in particular for the spaces betweenthe teeth of a toothed rack.
 10. The signal inducing device according toclaim 1, wherein the first material and the second material areconnected to each other by means of a force-fit connection and/or aform-locking connection and/or a positive substance locking connection.11. The signal inducing device according to claim 1, wherein the firstmaterial and/or the second material are spaced evenly and/or in that thefirst material and/or the second material are spaced in a specialencoding arrangement and/or in that the signal inducing device, inparticular the first material and/or the second material is/are designedand/or arranged in a way that the magnetic interaction surface producesan essentially binary signal.
 12. A signal inducing arrangement,comprising a sensor device and a signal inducing device according toclaim
 1. 13. The signal inducing device according to claim 2, whereinessentially all exposed surfaces of the signal inducing device show anessentially smooth surface, in particular with respect to the standardmoving direction of the signal inducing device.
 14. The signal inducingdevice according to claim 2, wherein the magnetic interaction surface isdesigned as a closed surface, in particular as a rounded surface,preferably as a circular surface and/or in that the signal inducingdevice is designed as a ring-like object and/or a wheel-like object. 15.The signal inducing device according to claim 3, wherein the magneticinteraction surface is designed as a closed surface, in particular as arounded surface, preferably as a circular surface and/or in that thesignal inducing device is designed as a ring-like object and/or awheel-like object.
 16. The signal inducing device according to claim 2,wherein the signal inducing device is essentially symmetrical,preferably mirror symmetrically, in particular with respect to geometryand/or with respect to magnetic behaviour, and/or in particular withrespect to a plane that lies normal to the standard moving direction ofthe signal inducing device and/or the standard moving direction of themagnetic interaction surface.
 17. The signal inducing device accordingto claim 3, wherein the signal inducing device is essentiallysymmetrical, preferably mirror symmetrically, in particular with respectto geometry and/or with respect to magnetic behaviour, and/or inparticular with respect to a plane that lies normal to the standardmoving direction of the signal inducing device and/or the standardmoving direction of the magnetic interaction surface.
 18. The signalinducing device according to claim 4, wherein the signal inducing deviceis essentially symmetrical, preferably mirror symmetrically, inparticular with respect to geometry and/or with respect to magneticbehaviour, and/or in particular with respect to a plane that lies normalto the standard moving direction of the signal inducing device and/orthe standard moving direction of the magnetic interaction surface. 19.The signal inducing device according to claim 2, wherein bulges and/ornotches are arranged along an exposed surface of the signal inducingdevice, preferably along the magnetic interaction surface, whereinpreferably said bulges and/or notches are arranged in a way that theyshow an essentially smooth surface with respect to the standard movingdirection of the signal inducing device and/or the magnetic interactionsurface.
 20. The signal inducing device according to claim 3, whereinbulges and/or notches are arranged along an exposed surface of thesignal inducing device, preferably along the magnetic interactionsurface, wherein preferably said bulges and/or notches are arranged in away that they show an essentially smooth surface with respect to thestandard moving direction of the signal inducing device and/or themagnetic interaction surface.